For the effective operation of dynamoelectric machines, it is desirable to assemble the stator and rotor parts so that they have free relative rotational motion with only a small controlled annular air gap between them. For a given cylindrical stator bore and rotor envelope combination, the uniformity of the air gap dimension of the stator and rotor when assembled depends upon their concentricity.
An obvious way of achieving the desired concentricity is by assembling the machine from parts having dimensional tolerances which when combined in the assembly of the machine result in an air gap of acceptable size and uniformity. This method tends to become increasingly expensive and difficult as the acceptable concentricity tolerances are reduced.
Another known method of assembling such machines so their rotor and stator elements have the desired degree of concentricity is disclosed in U.S. Pat. No. 3,165,816. Briefly, in this method of assembling dynamoelectric machines, the rotor and stator elements are axially aligned with an acceptable air gap and measure of concentricity and held in fixed relationship by spacing means such as shims inserted into the annular gap between the elements. The required number of rotor shaft bearings are each mounted in fixed relationship on rotor supporting means.
Each rotor supporting means is then loosely assembled adjacent the stator element, with surfaces of the rotor supporting means being in generally non-supporting and overlapping relation with corresponding surfaces of the stator element, and with the bearing carried by the supporting means fitted on the rotor shaft. Adhesive bonding means is provided in its plastic state between the associated overlapping surfaces of the stator element and the rotor supporting means. The bonding material permits relative movement between the overlapping surfaces as the shaft aligns the bearings with it.
When the bonding means is hardened enough to hold the stator and rotor elements in a fixed relationship, the spacing means are removed from the air gap leaving the rotor and stator elements freely rotatable and generally concentric with respect to each other, and the rotor shaft and bearings freely rotatable and accurately aligned relative to one another.